code: def test_neg_object(self, df, expected):
      # GH#21380
      df = pd.DataFrame({"a": df})
      expected = pd.DataFrame({"a": expected})
      tm.assert_frame_equal(-df, expected)
      tm.assert_series_equal(-df["a"], expected["a"])
  
file_path: pandas/pandas/tests/frame/test_unary.py
imports: from decimal import Decimal
  import numpy
  import pytest
  from pandas.compat.numpy import np_version_gte1p25
  import pandas
  import pandas._testing
label_desc: Use image node_id 2 for calling the TestDataFrameUnaryOperators obj's underlying member method code with example usage: obj.test_neg_object(df, expected) without return types